linux — security advisory
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: fix VM_PAT handling in COW mappings PAT handling won't do the right thing in COW mappings: the first PTE (or, in fact, all PTEs) can be replaced during write faults to point at anon folios. Reliably recovering the correct PFN and cachemode using follow_phys() from PTEs will not work in COW mappings. Using follow_phys(), we might just get the address+protection of the anon folio (which is very wrong), or fail on swap/nonswap entries, failing follow_phys() and triggering a WARN_ON_ONCE() in untrack_pfn() and track_pfn_copy(), not properly calling free_pfn_range(). In free_pfn_range(), we either wouldn't call memtype_free() or would call it with the wrong range, possibly leaking memory. To fix that, let's update follow_phys() to refuse returning anon folios, and fallback to using the stored PFN inside vma->vm_pgoff for COW mappings if we run into that. We will now properly handle untrack_pfn() with COW mappings, where we don't need the cachemode. We'll have to fail fork()->track_pfn_copy() if the first page was replaced by an anon folio, though: we'd have to store the cachemode in the VMA to make this work, likely growing the VMA size. For now, lets keep it simple and let track_pfn_copy() just fail in that case: it would have failed in the past with swap/nonswap entries already, and it would have done the wrong thing with anon folios. Simple reproducer to trigger the WARN_ON_ONCE() in untrack_pfn():
- Products
- linux
- Affected versions
- 6.1.27-1, 6.1.37-1, 6.1.38-1, 6.1.38-2, 6.1.38-2~bpo11+1, 6.1.38-3, 6.1.38-4, 6.1.38-4~bpo11+1, 6.1.52-1, 6.1.55-1, 6.1.55-1~bpo11+1, 6.1.64-1, 6.1.66-1, 6.1.67-1, 6.1.69-1, 6.1.69-1~bpo11+1, 6.1.76-1, 6.1.76-1~bpo11+1, 6.1.82-1
- Fixed versions
- 6.1.85-1, 6.8.9-1
- CVEs
- CVE-2024-35877
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 30 Oct 2026, 16:16 UTC · Revision 1
Source evidence
In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: fix VM_PAT handling in COW mappings PAT handling won't do the right thing in COW mappings: the first PTE (or, in fact, all PTEs) can be replaced during write faults to point at anon folios. Reliably recovering the correct PFN and cachemode using follow_phys() from PTEs will not work in COW mappings. Using follow_phys(), we might just get the address+protection of the anon folio (which is very wrong), or fail on swap/nonswap entries, failing follow_phys() and triggering a WARN_ON_ONCE() in untrack_pfn() and track_pfn_copy(), not properly calling free_pfn_range(). In free_pfn_range(), we either wouldn't call memtype_free() or would call it with the wrong range, possibly leaking memory. To fix that, let's update follow_phys() to refuse returning anon folios, and fallback to using the stored PFN inside vma->vm_pgoff for COW mappings if we run into that. We will now properly handle untrack_pfn() with COW mappings, where we don't need the cachemode. We'll have to fail fork()->track_pfn_copy() if the first page was replaced by an anon folio, though: we'd have to store the cachemode in the VMA to make this work, likely growing the VMA size. For now, lets keep it simple and let track_pfn_copy() just fail in that case: it would have failed in the past with swap/nonswap entries already, and it would have done the wrong thing with anon folios. Simple reproducer to trigger the WARN_ON_ONCE() in untrack_pfn():
osv:DEBIAN-CVE-2024-35877
linux
Fixed versions: 6.1.85-1
linux
Fixed versions: 6.8.9-1
linux
Fixed versions: 6.8.9-1
Complete source record
{
"id": "d4dde79545c6943e79a7d3c759167878fa2b5fa447db310aeb5f8323915de85a",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2024-35877",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2024-35877",
"summary": "In the Linux kernel, the following vulnerability has been resolved: x86/mm/pat: fix VM_PAT handling in COW mappings PAT handling won't do the right thing in COW mappings: the first PTE (or, in fact, all PTEs) can be replaced during write faults to point at anon folios. Reliably recovering the correct PFN and cachemode using follow_phys() from PTEs will not work in COW mappings. Using follow_phys(), we might just get the address+protection of the anon folio (which is very wrong), or fail on swap/nonswap entries, failing follow_phys() and triggering a WARN_ON_ONCE() in untrack_pfn() and track_pfn_copy(), not properly calling free_pfn_range(). In free_pfn_range(), we either wouldn't call memtype_free() or would call it with the wrong range, possibly leaking memory. To fix that, let's update follow_phys() to refuse returning anon folios, and fallback to using the stored PFN inside vma->vm_pgoff for COW mappings if we run into that. We will now properly handle untrack_pfn() with COW mappings, where we don't need the cachemode. We'll have to fail fork()->track_pfn_copy() if the first page was replaced by an anon folio, though: we'd have to store the cachemode in the VMA to make this work, likely growing the VMA size. For now, lets keep it simple and let track_pfn_copy() just fail in that case: it would have failed in the past with swap/nonswap entries already, and it would have done the wrong thing with anon folios. Simple reproducer to trigger the WARN_ON_ONCE() in untrack_pfn(): ",
"evidence": "osv:DEBIAN-CVE-2024-35877",
"products": [
{
"name": {
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{
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"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
"value": "6.1.38-2",
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},
{
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"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
"value": "6.1.52-1",
"evidence": "/affected/0/versions"
},
{
"value": "6.1.55-1",
"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
"value": "6.1.64-1",
"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
"value": "6.1.67-1",
"evidence": "/affected/0/versions"
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{
"value": "6.1.69-1",
"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
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{
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{
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"evidence": "/affected/1/package/name"
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"prerequisites": [],
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"evidence": "/affected/1/ranges"
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"affected_versions": []
},
{
"name": {
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"fixed_versions": [
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],
"affected_versions": []
}
],
"severity": "medium",
"structured": {
"id": "DEBIAN-CVE-2024-35877",
"aliases": [
"DEBIAN-CVE-2024-35877"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
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"events": [
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{
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],
"package": {
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"purl": "pkg:deb/debian/linux?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
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"6.1.37-1",
"6.1.38-1",
"6.1.38-2",
"6.1.38-2~bpo11+1",
"6.1.38-3",
"6.1.38-4",
"6.1.38-4~bpo11+1",
"6.1.52-1",
"6.1.55-1",
"6.1.55-1~bpo11+1",
"6.1.64-1",
"6.1.66-1",
"6.1.67-1",
"6.1.69-1",
"6.1.69-1~bpo11+1",
"6.1.76-1",
"6.1.76-1~bpo11+1",
"6.1.82-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2024-35877.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "6.8.9-1"
}
]
}
],
"package": {
"name": "linux",
"purl": "pkg:deb/debian/linux?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2024-35877.json"
},
"ecosystem_specific": {
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}
},
{
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],
"package": {
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},
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2024-35877.json"
},
"ecosystem_specific": {
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}
}
],
"modified": "2026-10-15T09:47:27.787714306Z",
"provider": "osv",
"upstream": [
"CVE-2024-35877"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2024-35877"
]
},
"related_cves": [
{
"value": "CVE-2024-35877",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 327364,
"published_at": "2024-05-19T09:15:08.99+00:00"
}